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Driving along in Light traffic, 100kph, 30C, Efan On. Needle is sitting right at the top of the N. Maybe a touch above. I thought it higher than it should be, not bad, just odd. For some reason I switched off the efan. Needle iimidiately dropped to just above the bottom of the N. Right where I’d expect it to be in these conditions.
My car's temp needle moves up or down a good 1/8th of an inch immediately if I turn anything on/off, like even the fan on medium. Far too quick to reflect an actual increase or decrease in temps. It could be nothing more then a voltage issue affecting the gauge needle way too much. Can you replicate this while idling? Like say..for example.. using jumpers to attach a dead battery to your running car and see if that draw causes the gauges to move around?
What about just the current draw possibly causing the instruments to lose some ground connection? Check your terminals. Might just be an electrical gremlin. Without a PROPER temperature gauge running independantly of the instrument cluster, it can be hard to justify if the temperature increase is just a gremlin or if it actually IS a problem...
Certainly could be voltage change, but turning OFF a 17amp pull would make it rise if it were running low voltage right?
The drop I saw appeared to be a real reduction in temp. Not instantly. That was a poor word choice. It dropped over two seconds.
Im on other unrelated issues today. Four new injectors, a nos Vintage Performance GM module for the amp and a replacement vac advance unit. If it happens again after all that I’ll follow up with more details.
At 100 km/h you shouldn't need a fan, the fan can actually act to block some air going through the rad. Can you replicate the drive with the fan off and see what happens? Or try driving with the fan off and then switch it on and see if the temp increases?